1. Field of the Invention
This invention relates to a radiation curable resin composition for use in magnetic recording media which is especially characterized by permitting good dispersion of magnetic powders and forming a highly durable cured film.
2. Description of the Prior Art
Radiation curable resin compositions have the advantage of being capable of low-temperature cure and short-time cure, and are being used in various applications. For example, a large number of radiation curable resin compositions having a variety of excellent properties, such as curing rate, surface hardness and surface smoothness of the cured resin, toughness of the cured film, and the like, have been developed and are being widely used as coating materials for plastics, metals, wood, paper and the like.
Moreover, owing to the above-described advantage, radiation curable resin compositions are also being used as materials for the formation of magnetic recording media and, in particular, for the formation of a resin layer having a magnetic powder dispersed therein, on a substrate comprising a film or sheet formed of a resin.
However, radiation curable resin compositions have poor dispersibility therein inorganic fine powders such as magnetic powders, as compared with thermoplastic type and thermosetting type resin compositions. Accordingly, in order to use radiation curable resin compositions in the formation of magnetic recording media, it is necessary to improve their dispersibility.
As a means for improving the dispersibility of radiation curable resin compositions, it is conventionally known to add thereto a dispersing agent comprising, for example, a polymer having good dispersibility. On the basis of this conception, some radiation curable resin compositions having improved dispersibility of inorganic fine powders therein have been developed and put to practical use.
However, the polymer added as a dispersing agent for the improvement of dispersing power is an inert material not participating in crosslinking reactions. Thus, its addition has the disadvantage of impairing the curing rate of the resulting resin composition and the properties, such as durability and others, of the magnetic recording media formed therewith.